Process of forging hollow metal blanks



Feb. 16, 1937. Y E. GIACCHINO 2,070,589

PROCESS OF FQRGING HOLLOW METAL BLANKS I Filed Aug. 31., 1933 "Fi .1 iy/ .2.

Patented Feb. 16, 1937 UNITED STATES 2,070,589 v PROCESS or roncmcnoLLow' METAL BLANKS Ezio Giacchino, Brussels, Belgium; Francesca.Teresa Bebaldo Giacchino, Aldo Giacchino, and Ezio Giacchino, Jr., soleheirs of Ezio Giacchino, Sr., deceased, assignors, by direct and mesneassignments, to Socit Anonyme Forgeage Electrique Giacchino, Brussels,Belglum, a Belgian company Application August 31, 1933, Serial No.687,693

In Belgium July 4, 1933 3 Claims. (Cl. 29-15611) My invention relates toa process for shaping and forging metal stock and it has for its objectto shape or forge hollow metal bodies of varying inner cross-section,with the use of a fuel or of electrical energy as heating agent.

A particular object of my invention is to make hollow metal'bodies offlaring cross-section, such bodies being very diilicult to shape by theusual processes, as is the case with some valves for the engines offlying machines.

In accordance with my invention I obtain this result in a very simpleand reliable manner by heating a hollow or a tubular blank over asuitable length and expanding by internal pressure the portion thereofwhich has been softened by heat. To apply such internal pressure,various means may be resorted to.

In one embodiment of my invention, I'exert the required internalpressure by means of a deformable core forced into the tubular .blank.which core may suitably be formed of a loose material oflow electricconductivity infusible at f forging temperature, preferably graphitepowder.

Preferabiythe tubular blank is. closed at the end which is to beexpanded, the closure then consisting of a bottom wall integral with theblank and inwardly rounded at the corners to prevent the formation ofcracks.

The mere expansion of the blank by the means above referred to makes itpossible to obtain a part which can be subsequently finished in a press.It is however also possible to shape directly the part to the requisiteform and size, by expanding it in a suitable die. r

The effect of expansion on the heated blank may.v create a tendency for'a wall thereof to stretch andbecome locally thinner. If it is desired toobtain uniform wall thickness, I may apply during the forging operation,an axial pressure on the blank in order to feed metal to the expandedportion and thus give said portion Y ent application Ser. No. 687,694 ofeven date herewith.

In order that the various features of my improved process and itsadvantages may be more fully understood, reference will be had to theaccompanying drawing in which the steps of forging a hollow valve bodyare diagrammatically illustrated by way of example.

In the drawing:

Fig. 1 is a-sectional elevation of'thlehollow 10 valve body.

Fig. 2 is a similar view of the blank from which it is forged. Figs. 3 m6 are similar sectional views illustrating the blank in successivestages of the 15 forging operation. 1

Fig. 7 isa sectional elevation showing the method of forging the samevalve in a die.

In order to forge a valve body such as shown in Fig. 1, the usualprocess starts from a, solid blank I of substantially the same diameteras the enlarged portion of the valve. In this blank a hole is bored,with a diameter corresponding to the inner diameter a. of the" enlargedportion, whereupon said portion is forged and the stem is contracted toits final diameter d. This methodhas several inconveniences; the size ofthe hollow and the wall thickness vary considerably from one piece tothe other; the operation furthermore is slow, diiiicult and expensive.30

With my improved process these inconveniences-are completely avoided. Istart from a tubular blank 2 having an'outer diameter-d'and an innerdiameter c equal to the outer diameter and inner diameter, respectively,'of the valve In the hole in the blank, the end of which is preferablyrounded to avoid the formation of cracks, I insert a suitable loose orplastic ma-. terial 3, as powdered graphite for example (Fig. 3). Thisgraphite is well packed in order-that" its volume shall remainsubstantially uniform. in the course of forging.

In order to enlarge the hollow within the blank, I heat the blankelectrically over afgiven length a: from its closed end. Atfthe sametime, or immediately thereafter, I exert a pressure p on the core 3(Fig. 4) thereby creating within the blank an internal pressure adaptedto swell the portion a: which has been .softened by heat (Fig. 5).

If, while the expanding pressure p is exerted on the core, I app yon one'of the ends of the .blank an axial pressure in the'direction of ar- 55stem, said blank being closed at one end (Fig. 2)

row 1 or 11' (Fig. 4) this pressure assists in causing the wall to bendoutwardly at z, and furthermore it causes metal to be fed to thatportion of the wall, whereby the thickne..s of this bent or expandedportion will be caused to remain substantially uniform.

A form of blank such as shown in Fig. 6 is thus obtained. This caneasily be stamped or pressed between suitable dies to the final shapeillustrated in Fig. 1. By suitably controlling the application of heat,as the heating temperature, the place and the size of the heatedportion, and by adjusting the pressures p and y or 1! I am enabled tovary according to requirements, in the course of the operation, the formor size of the swelling and the thickness of its walls.

In the example shown in Fig. 'I, the end of the hollow blank {which is'to-be enlarged is provided with a core 3 and heated, whereupon it ispromptly placed into a die 4 and a pressure p is exerted on the core. Onexpanding, the blank -2 then is caused to take up the shape of the die.In this case also an axial pressure as 11 may be exerted on the blank inorder to force metal to feed the expanded portion.

It ill be understood that'my improved process can be used for forginghollow bodies of various forms either from blanks having a closed end,as shown, or from tubular blanks open 'at both ends. In the latter casea suitable stop or abutment may be provided for holding the core usedfor expanding the blank.

I claim: 1.' In a process of forging hollow metal bodi in-a tubularblank, applying an electric heatin current to a portion of said blank tosoften the metal forming arch portion, applying pressure to said core toexpand said softened portion, simultaneously applying axial pressure tosaid blank, and controlling the shape of the expanding blank by varyingthe application of heat and the relative pressures on saidcore and onsaid blank.

2. Those steps in the process of forging hollow' metal bodies whichconsist in inserting a deformable core in a tubular blank, applying heatto a portion of the blank to soften the metal forming said portion,applying pressure to the core to expand the softened portion,simultaneously applying axial pressure to the blank, and controlling theshape of the expanding blank by varying the application of heat and byindependsure to the core to expand the softened portion,

simultaneously applying axial pressure to the blank, and controlling theshape of the expanding blank by controlling the application of heat andalso by independently controlling thepressureexertedonthecoreandontheblank.

-- mo 'GIACCHINO.

